/* Copyright (c) 2011-2013 GoPivotal, Inc. All Rights Reserved. Licensed under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language governing permissions and limitations under the
 * License. */
package com.ltmap.common.utils;

import java.util.HashMap;
import java.util.Map;
import java.util.UUID;

/**
 * Helper for creating random and Type 1 (time-based) UUIDs.
 * Company:天人环境<br>
 * @author WangXu<br>
 * @version Revision: 1.0
 */
public class UUIDUtils {

	 final static char[] digits = { '0', '1', '2', '3', '4', '5', '6', '7', '8',  
	            '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',  
	            'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y',  
	            'z', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',  
	            'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y',  
	            'Z' };  
	  
	    final static Map<Character, Integer> digitMap = new HashMap<Character, Integer>();  
	  
	    static {  
	        for (int i = 0; i < digits.length; i++) {  
	            digitMap.put(digits[i], i);  
	        }  
	    }  
	  
	    /** 
	     * 支持的最大进制数 
	     */  
	    public static final int MAX_RADIX = digits.length;  
	  
	    /** 
	     * 支持的最小进制数 
	     */  
	    public static final int MIN_RADIX = 2;  
	  
	    /** 
	     * 将长整型数值转换为指定的进制数（最大支持62进制，字母数字已经用尽） 
	     *  
	     * @param i 
	     * @param radix 
	     * @return 
	     */  
	    public static String toString(long i, int radix) {  
	        if (radix < MIN_RADIX || radix > MAX_RADIX)  
	            radix = 10;  
	        if (radix == 10)  
	            return Long.toString(i);  
	  
	        final int size = 65;  
	        int charPos = 64;  
	  
	        char[] buf = new char[size];  
	        boolean negative = (i < 0);  
	  
	        if (!negative) {  
	            i = -i;  
	        }  
	  
	        while (i <= -radix) {  
	            buf[charPos--] = digits[(int) (-(i % radix))];  
	            i = i / radix;  
	        }  
	        buf[charPos] = digits[(int) (-i)];  
	  
	        if (negative) {  
	            buf[--charPos] = '-';  
	        }  
	  
	        return new String(buf, charPos, (size - charPos));  
	    }  
	  
	    static NumberFormatException forInputString(String s) {  
	        return new NumberFormatException("For input string: \"" + s + "\"");  
	    }  
	  
	    /** 
	     * 将字符串转换为长整型数字 
	     *  
	     * @param s 
	     *            数字字符串 
	     * @param radix 
	     *            进制数 
	     * @return 
	     */  
	    public static long toNumber(String s, int radix) {  
	        if (s == null) {  
	            throw new NumberFormatException("null");  
	        }  
	  
	        if (radix < MIN_RADIX) {  
	            throw new NumberFormatException("radix " + radix  
	                    + " less than Numbers.MIN_RADIX");  
	        }  
	        if (radix > MAX_RADIX) {  
	            throw new NumberFormatException("radix " + radix  
	                    + " greater than Numbers.MAX_RADIX");  
	        }  
	  
	        long result = 0;  
	        boolean negative = false;  
	        int i = 0, len = s.length();  
	        long limit = -Long.MAX_VALUE;  
	        long multmin;  
	        Integer digit;  
	  
	        if (len > 0) {  
	            char firstChar = s.charAt(0);  
	            if (firstChar < '0') {  
	                if (firstChar == '-') {  
	                    negative = true;  
	                    limit = Long.MIN_VALUE;  
	                } else if (firstChar != '+')  
	                    throw forInputString(s);  
	  
	                if (len == 1) {  
	                    throw forInputString(s);  
	                }  
	                i++;  
	            }  
	            multmin = limit / radix;  
	            while (i < len) {  
	                digit = digitMap.get(s.charAt(i++));  
	                if (digit == null) {  
	                    throw forInputString(s);  
	                }  
	                if (digit < 0) {  
	                    throw forInputString(s);  
	                }  
	                if (result < multmin) {  
	                    throw forInputString(s);  
	                }  
	                result *= radix;  
	                if (result < limit + digit) {  
	                    throw forInputString(s);  
	                }  
	                result -= digit;  
	            }  
	        } else {  
	            throw forInputString(s);  
	        }  
	        return negative ? result : -result;  
	    }  
	    
	    private static String digits(long val, int digits) {  
	        long hi = 1L << (digits * 4);  
	        return UUIDUtils.toString(hi | (val & (hi - 1)), UUIDUtils.MAX_RADIX)  
	                .substring(1);  
	    }  
	      
	    /** 
	     * 以62进制（字母加数字）生成19位UUID，最短的UUID 
	     *  
	     * @return 
	     */  
	    public static String create() {  
	        UUID uuid = UUID.randomUUID();  
	        StringBuilder sb = new StringBuilder();  
	        sb.append(digits(uuid.getMostSignificantBits() >> 32, 8));  
	        sb.append(digits(uuid.getMostSignificantBits() >> 16, 4));  
	        sb.append(digits(uuid.getMostSignificantBits(), 4));  
	        sb.append(digits(uuid.getLeastSignificantBits() >> 48, 4));  
	        sb.append(digits(uuid.getLeastSignificantBits(), 12));  
	        return sb.toString();  
	    }  

}
